Scores of bush fires were yesterday still burning out of control around Sydney and across Australia's most populous state.

Fire officials believe most were deliberately lit and strong winds have continued to fan the flames which have destroyed homes, isolated towns and cut major highways across the state of New South Wales and around Sydney.

Hundreds of extra firefighters from neighbouring Victoria state have been called in to join almost 5,000 emergency workers, hundreds of whom have been battling fires for five days.

No fatalities have been reported but a fire brigade officer was injured yesterday when a roof collapsed on him and dozens of others have suffered minor injuries.

Dry conditions and winds gusting up to 55mph and temperatures above 35C (95F) have left fire crews helpless to contain the flames.

New South Wales fire chief Phil Koperberg said some of the fires had been caused by lightning, but others had been deliberately lit.

Though not as extensive as the devastating blazes of Christmas 1994 when four people were killed as 284 bush fires flared across the state, the winds had propelled the fire fronts at unprecedented speeds.

"We have had what is effectively history-making behaviour," Mr Koperberg said. "We have never seen anything like that before."

Sydney has been left blanketed by brown haze and ringed by fires.

"All around the perimeter of the metropolitan area, west and south west and indeed down the south coast and many other areas, there are fires that have the capacity to flare up again should the wind pick up," said state emergency services minister Bob Debus.

More than 2,000 people have been evacuated from homes. About 80 properties had been destroyed around Sydney.

Firefighters were no longer attempting to contain the blazes but concentrating on saving lives and property.

With a major blaze now hitting beachside residential areas 31 miles south of Sydney around the town of Helensburgh, firefighters faced the prospect of a solid wall of flame more than 35 miles wide, Mr Koperberg said.

Around 1,500 people were evacuated from Helensburgh overnight along with most of the nearby southern Sydney suburb of Waterfall before the local public school burned down.

Strong winds were likely to continue to fan fires today but temperatures have fallen to below 30C (86F).

Meteorologist Rob Webb said winds were expected to pick up to around 25mph to 35mph during the day.

But Mr Webb said temperatures were expected to again soar in some regions by the end of the week.